> ## Documentation Index
> Fetch the complete documentation index at: https://www.docs.forgeshipyard.com/llms.txt
> Use this file to discover all available pages before exploring further.

# L3 · CAD & Geometry World Model

> The deterministic geometry service. The AI never computes geometry itself.

<Note>
  **In plain terms:** Anything involving a real measurement (a clearance, a clash, a
  tolerance) is computed here by deterministic geometry tools, not by the AI. The AI
  is good at language and bad at geometry, and Forge enforces that distinction by
  design.
</Note>

## What it does

L3 computes geometry facts deterministically: clearance checks, clash detection,
dimensional tolerances, module boundaries, and weight estimates from geometry. All
of these are computed by L3, never by a language model.

## The single most structural rule in Forge

> Any numeric geometry claim must cite a measurement result from L3.

If the AI wants to assert "the clearance is 47 millimeters," it must cite a
measurement record that says so. If no such record exists, the claim is rejected at
the verification stage.

Language models are good at language; they are bad at geometry. The architecture
enforces that distinction **structurally, not by hope.** A language model may only
cite measurement results that already exist; it may never produce them.

## What L3 outputs

* `measurement_result`
* `clash_result`
* `clearance_result`
* `tolerance_check`
* `module_boundary`

## Why this matters for trust

This is the rule that prevents the most dangerous failure mode: an AI confidently
stating a number that sounds right but is not grounded in any real measurement. By
forcing every numeric geometry claim to point to a real measurement record, Forge
makes that class of fabrication impossible to slip through. The system targets 100%
on this: every numeric geometry claim cites a real measurement result.